The present invention relates to a vibration pickup with a pressure sleeve.
Vibration pickups of the above mentioned general type are known in the art. One of such vibration pickups with a pressure sleeve is disclosed in the German patent document DE 44 03 660. It is formed as a knock sensor for monitoring the operation of an internal combustion engine of a motor vehicle. The pressure sleeve is placed through an abutment region firmly on a component which causes a vibration, here a motor block of the internal combustion engine.
The vibrations to be detected in the known arrangement are represented by knocking noise of the internal combustion engine during the operation. They are transmitted through the pressure sleeve in a piezo-ceramic disc as a sensor element, with the intermediately located contact discs and insulating discs. It allows a signal pickup, and thereby an evaluatable electric output signal is produced. The type of mounting or clamping of the sensor arrangement on the pressure sleeve and the mounting of the vibration pickup on the component to be vibrated has a great influence both on the manufacture procedure as well as on eventual correct or faulty measurements and disturbances in the operation. The clamping of the sensor element together with a plurality of individual components, for example with a spring and a seismic mass, is performed in the known vibration pickup for example by a threaded ring which is screwable on a corresponding thread of the pressure sleeve.
Another German document DE 195 24 147 discloses a vibration pickup of the above mentioned general type in which the threaded ring and the spring as a so-called spring head nut are formed as a single one-piece component. This spring head nut is then screwable on the thread of the pressure sleeve and abuts directly against the seismic mass.
Accordingly, it is an object of present invention to provide a vibration pickup of the above mentioned general type which is a further improvement of the existing vibration pickups.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a vibration pickup with a pressure sleeve which has to be arranged on a component causing the vibrations and a sensor element which detects the vibrations, wherein in accordance with the present invention the seismic mass and the pressure sleeve together form a one-piece integral component.
The seismic mass is located outside the pressure sleeve under an actual pretensioning on an abutment surface of the sensor element and thereby the sensor element is held between the seismic mass and a flange-shaped segment of the pressure sleeve. This provides, because of the one-piece integral arrangement, a simplification of the total construction of the vibration pickup a with reduced number of the components.
With the one-piece integral construction, the seismic mass in a simple manner is connected with the pressure sleeve through a web which is flexible within predetermined limits. Therefore between the seismic mass and the flange-shaped projection a ring gap is formed. Before mounting of the sensor element, it must have a substantially smaller axial opening than the axial width of the sensor element.
For providing a simple mounting of the sensor element, the sensor element is axially slotted on one side, so that during the mounting of the vibration pickup it is placeable around the periphery on the pressure sleeve in the ring gap. Thereby during the mounting of the sensor element and the pressure sleeve, the seismic mass is pressed back in an axial direction from the flange-shaped projection, so that the sensor element passes in the thusly increased ring gap. After the mounting, the sensor element is held with the required pretensioning on the flange-shaped projection.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.